Update cstring_view to latest exemplar

- Make cstring_view an INTERFACE-based library
- Bring cstring_view the new JSON-based CI framework
- Add some missing SPDX license identifiers
- Update the README to contain the latest language and a compiler support table
- Update the CMake installation logic to the latest version
- Slightly adjust the implementation of the default constructor for C++20 compatibility

Author: ednolan

.clang-format

@@ -125,7 +125,7 @@ IndentCaseBlocks: false
 IndentCaseLabels: false
 IndentExternBlock: AfterExternBlock
 IndentGotoLabels: true
-IndentPPDirectives: None
+IndentPPDirectives: BeforeHash
 IndentRequiresClause: true
 IndentWidth:     4
 IndentWrappedFunctionNames: false

.devcontainer/devcontainer.json

@@ -0,0 +1,5 @@
+infra/** linguist-vendored
+cookiecutter/** linguist-vendored
+*.bib -linguist-detectable
+*.tex -linguist-detectable
+papers/* linguist-documentation

.gitattributes

@@ -1,71 +1,5 @@
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